Facultative waste stabilization lagoons are currently the predominant tool for the treatment of wastewater by sanitation and public health professionals. Facultative refers to the ability of the bacteria typically used in sewage treatment/waste stabilization to live under more than one set of environmental conditions. Facultative bacteria are useful as they can tolerate the varying physical and chemical conditions resulting from changes in the bodies of water over time, such as when animal waste or plant matter degrades.
Commercial catfish ponds, constructed for the breeding and production of catfish, and other man-made bodies of water typically follow a design similar to facultative waste stabilization lagoons and thus experience many common problems.
Facultative waste stabilization lagoons utilize aerobic and facultative bacteria to stabilize organic waste materials. An adequate on-going supply of oxygen to the body of water is essential in order for the bacteria to perform the stabilization function. Originally, the designers of facultative waste stabilization lagoons, commercial catfish ponds, and other bodies of water relied on the natural process of algal photosynthesis on and below the surface of the water to supply this essential oxygen.
However, repeated experience has shown that various climatic conditions and other external and internal factors may sometimes inhibit the process of algal photosynthesis to the point that the ongoing supply of oxygen to the body of water is inadequate.
Most commonly, this occurs during the warmer months of the year when an overgrowth of algae can occur on the water surface, resulting in filamentous algae mats on the surface which block the radiation of sunlight into the water. In the absence of such sunlight, photosynthesis cannot take place and thus the production of oxygen below the surface is inhibited.
In severe cases, this set of factors causes a septic condition in the body of water in which the biological system within the body of water becomes anaerobic. This phenomenon can eventually result in the release of offensive odors from the lagoon and in the lagoon's failure to meet regulatory effluent limits on the organic discharge from these facilities.
These septic conditions can also occur during cooler months when limited intervals of sunlight result in an inadequate rate of algal photosynthesis. In the context of commercial catfish ponds, these septic conditions can quickly result in the death of the entire fish population.
In response to these problems, inventors previously have created several types of devices to mechanically and/or chemically aerate facultative waste stabilization lagoons, commercial catfish ponds, and similar bodies of water.
U.S. Pat. No. 4,409,107 to Busch discloses a fixed position aerating device which uses a paddlewheel with rotatable paddles to agitate the water near the surface to mix oxygen-rich surface water with oxygen-deficient deep water; however, this device must be moored to the bank of the body of water and hence can only aerate the small area within a narrow radius of the aerator's fixed position. It also does not break up algae masses on the surface.
U.S. Pat. No. 4,680,148 to Arbisi et al. shows an unmanned mobile pond aerating vessel whose movement and position are controlled by a complex microprocessor and beam transmitting/receiving system. The Arbisi device is powered by an electric motor which necessitates the expense and availability of a three-phase power line or other suitable electric power source in close proximity to the pond. Moreover, the unmanned Arbisi vessel cannot be utilized in a pond until trained personnel have programmed the microprocessor in a manner suitable for the particular pond in question; and the complexity of the electronic circuitry and microprocessor render construction and use of the device expensive. These features likely render actual use of the Arbisi vessel overly complicated and time-consuming. Furthermore, Arbisi discloses no mechanism for dispensing chemical agents into the water which, under certain circumstances, is a necessary complementary means of aeration.
U.S. Pat. No. 5,089,120 to Eberhardt broadly discloses a vessel with laterally adjustable pontoons adapted for dispensing into the water a treatment agent, such as lime, for neutralizing acid rain; however, this device fails to recognize the importance of mechanical aeration and surface agitation in combatting the problems outlined earlier. Specifically, the Eberhardt vessel lacks a paddlewheel or any similar device designed for breaking up algae mats in a manner sufficient to cause the submersion and decomposition of such mats. Eberhardt is also relatively large, complex, and expensive.
U.S. Pat. No. 4,268,398 to Shuck et al. discloses a sludge-agitating vessel mounted on pontoons. The Shuck device is designed for operation within a defined radius of a separate pumping station and is dependent on controlled air distribution and compression for carrying out its sludge treatment method. The Shuck device is intended specifically for agitating sludge toward a previously constructed pumping station and is unsuitable for portable use in aerating algae-infested lagoons or ponds absent such a pumping station at each required location.
U.S. Pat. No. 4,441,452 to Strain, Jr. shows a pumping apparatus to be attached to a tractor and backed into a pond to aerate the shallow areas at the edge of the pond. The Strain device is capable of mechanically aerating and destroying algae mats only within a small area radiating from the bank of the body of water.
U.S. Pat. No. 4,190,619 to Cherne discloses a liquid aerating rotor assembly which has a front scoop for preventing solid debris located in the surface layer of liquid form coming in contact with an aerating rotor.